1. Technical Field
The present invention relates to a surface emitting laser, an atomic oscillator, and a manufacturing method of a surface emitting laser.
2. Related Art
A surface emitting laser (a Vertical Cavity Surface Emitting Laser: VCSEL), for example, is used as a light source of an atomic oscillator using Coherent Population Trapping (CPT) which is one of quantum interference effects.
For example, in JP-A-2009-289907, a surface emitting laser including a first distribution Bragg reflector, a second distribution Bragg reflector, and an active layer disposed between the first distribution Bragg reflector and the second distribution Bragg reflector is disclosed. In the surface emitting laser of JP-A-2009-289907, at least one of the first distribution Bragg reflector and the second distribution Bragg reflector (DBR) includes a first layer formed of AlGaAs, and a second layer formed of AlGaAs of which an Al composition is lower than that of the first layer, and a decrease in emission intensity is suppressed by setting a carbon concentration in the first layer to be less than or equal to 1×1018 cm−3. In the surface emitting laser, it is important to suppress the decrease in the emission intensity, and thus there is a demand for a surface emitting laser having high reliability in which the decrease in the emission intensity is reduced.
Here, in JP-A-2009-289907 described above, it is disclosed that a correlation between the carbon concentration in the AlGaAs layer of the DBR and aging properties is obtained, and thus a surface emitting laser in which the decrease in the emission intensity is suppressed has been found. In contrast, the inventor has focused on a correlation between the surface roughness Ra of n-DBR and aging properties, and thus has achieved the invention.